The invention relates to a method for controlling the temperature of glow plugs of a combustion engine.
Various methods have been disclosed in the prior art for controlling glow plugs to a target temperature, for example in DE 10 2112 192 013 A1 and DE 10 2006 060 632 A1. A general problem associated with controlling the temperature of glow plugs consists in that the electrical resistance of glow plugs, especially of ceramic glow plugs, is subject to major fluctuations due to manufacturing tolerances. And since inaccuracies in the resistance temperature characteristic used lead to corresponding inaccuracies in the temperature control, it is desirable to obtain most accurate knowledge of the electrical resistance of a glow plug at a target temperature.
One option for determining the resistance temperature characteristic of a glow plug consists in keeping the engine at standstill for a few minutes and then heating the glow plug for a certain period of time, e.g. for approx. one minute using a constant amount of specified electrical power until the glow plug has reached a state of equilibrium, the temperature of which is defined by the heat output and the heat dissipation with the engine at standstill and is therefore known or can be ascertained for all future cases by way of measuring. This way of proceeding however has the disadvantage of being very expensive.